Method for orienting cores



J. M. PEARSON METHOD FOR ORIENTTNG comas Aug. 13, 1940.

Original Filed Nov. 5, 1937 2 Sheets-Sheet l Aug. 13, 1940. J. M PEARSQN2,211,158

METHOD FOR ORIENTING CORES Original Filed Nov. 5, 1937 2 Sheets-Sheet 2Patented Aug. 13, 1940 j UNI-TED s'm'rl-:sy

PATENT oFFlcE Sperry-Sun -Well Surveying Company, Philadelphia, Pa., acorporation of Delaware Original application November 5, 1937, SerialNo.

172,988. Divided and this application Septcmber13, 1938, Serial No.229,645

6 Claims.

This invention relates to a-method and apparatus for orienting cores bythe determination of the magnetic characteristics thereof.

This application is a division of my application Serial No. 172,988,flled November 5, 1937.

As described, for example, in Herrick Patent No. 1,792,639, datedFebruary 17, 1931, it is possible to determine to a fair degree ofaccuracy the dip and strike of strata penetrated by a bore hole ifmeasurements are made to ascertain the magnetic polarization of a coretaken at the location of the strata.

The assumption borne out by observations is that in a magneticallypolarized core the axis of polarization generally originally coincidedin direction and sense with the earths eld and that in a core showing anaxis of maximum susceptibility, that axis originally coincided indirection with the axis of the earths eld, though in the latter case thesusceptibility axis is without sign.

In vmaking such determinations, the magnetic polarity or axis of maximumsusceptibility of the core may be determined by means of an apparatus ofthe type generally disclosed in said Herrick patent, which, brieiiystated, constitutes a magnetometer capable of determiningthe magneticnorth or susceptibility axis of the core. The magnetic polarity orsusceptibility axis is marked on the core following the use of suchapparatus, and by suitable measurements there can .be then determinedthe apparent dip and strike of a bedding plane' appearing in the corewith respect to the magnetic northor susceptibilityl axis so indicated.Further calculations to determine the relation of dips and strikes totl. e earth may then be made, either numerically or by use of anapparatus such as that disclosed in my applicationl Serial No. 146,739,led June 7, 1937.

The present invention has two broad objects, rst the improvement ofapparatus for better determining the magnetic properties of cores andsecond an improved method of making determinations with such apparatus(including preparation of cores) whereby more thorough analysis of themagnetic properties of cores may be made than by methods heretoforeused.

The improved apparatus may be brieiiy outlined as comprising anastaticmagnet system, adjacent which the core may be mounted for slowrotation, together with a photographic recording means whereby movementsof the astatic magnet system may be accurately recorded over asubstantial period of time, the core rotating on its axis quite slowlyin View of the delicacy and consequent long period of the magnet system.The objects of the invention relating to the apparatus are particularlyconcerned with various arrangements and details whereby thedeterminations may be carried out with a high degree of accuracy andparticularly without influence due to extraneous magnetic elds.I Theinvention `also contemplates the provision in the apparatus of means foraccurately supporting the core so as to provide for repeatedobservations consistent with each other. The accomplishment of these andother objects relating to vthe apparatus will become clear from thedescription which follows.

The primary object of the invention'fwith .respect to the method is tocarry out measurements of the magnetic properties of cores in such vfashion that the various magnetic properties may be individuallydetermined and segregated from each other. -In most cores'it may besuspected that the vmagnetic properties m'ight result rst from denitepolarization, secondly from -a more or less uniform condition ofanisotropic susceptibility which may exhibit itself as a general axisfor the whole core and anistropic susceptibility or polarizationconditions, orboth, resulting from local inclusions in the core ofmaterials having magnetic properties diiering substantially from theproperties of the major portions thereof. If such a core is rotatedabout its axis through a single revolution below a suspended astaticmagnetic system in which the axes of the magnets are generally parallelto the axis of the core, the deection of the magnetic system as recordedon a tensitized paper in the type of apparatus herein described will bean irregular line probably having more or less sinusoidal form. Such aline constitutes arather uninterpretable record of the sum of thevarious `properties of the core. In accordance with the presentinvention a second record is made by turning the core end for end androtating it under the magnetic system, preferably (for simplicity ofgraphical calculation) in a direction opposite its former rotation.There is thus obtained another curve which, in general, may have littleresemblance to the one rst obtained.

-From. the two curves, however, polarization eiects may be readilysegregated from the eilects of anisotropic susceptibility, and in eachof the subdivisions of these elects there may be rather readilysegregated those portions of the effects which are of interest fromthose which are strictly characteristic of the particular core and notof interest. This latter analysis is particularly true if runs are madeon a series of cores taken close to each other in' the same portion ofthe bore hole. Furthermore, by taking proper precautions in making thedeterminations, other matters of interest are deducible.

The various objects of the invention relating to the preparation ofcores and the making of determinations and details of both methods andapparatus will be apparent from the following description read inconjunction with the accompanying drawings in which:

Figure l is a side elevation, partly in section, showing the generallayout of the improved apparatus;

Figure 2 is a wiring diagram illustrating the inner connections betweenvarious portions of the apparatus;

Figures 3, 4 and 5 are diagrams showing the types of records obtained inthe apparatus and their mode of analysis;

Figure 6 is a diagrammatic illustration of an alternative method ofmaking determinations; and

Figure 7 is a vertical section illustrating one method of preparingcores for determinations.

Referring first to Figure 1, the various portions of the apparatus areillustrated as supported upon a sturdy table 2 arranged to preventvibration to a maximum degree, and preferably carefully leveled toproperly support a magnetic system. The table carries a magnetic shield4, for example, of steel of considerable thickness, provided with aWindow at its lower end of suiiicient size to permit entry of a core andits holder. Fixed in the upper portion of this shield is a magnetometerhousing 6 consisting of a torsion wire enclosing tube and a lowerdamping housing 8, both formed of nonmagnetic material. Within thishousing there is located a pair of bar magnets I0 and I2, of equaldimensions and supported upon a suitable mounting carrying a mirror I4,the whole structure being supported by a torsion wire I6 of suitablelength adjustable about its axis by means, generally indicated at I8, ofthe type4 usually provided on sensitive galvanometers. Suchsuspensionsfor astatic magnetic systems are well known and need not be furtherdescribed. Windows are provided in the housing 6 and the shield 4opposite the face of the mirror. Extending downwardly through the tableis a tube 20 in which is slidably mounted a tube 22 carrying a coreholder and counter-balanced by weights 24 supported by pulleys 26. Arack 28 carried by the tube 22 acts as a spline with respect to thebearing portions of the tube 20 to prevent rotation of tube 22 about itsaxis. The teeth of this rack mesh with a pinion 30 adapted to be drivenby a hand wheel 34 through a shaft 32 arranged to be clamped in fixedposition by clamping means 38. The parts just described are accuratelyarrarmed so as to definitely align a core carried by the holder withrespect to the magnetic system.

'I'he core holder, which is described in detail in the parentapplication above referred to, comprises means for holding a core androtating it about an axis with its axis horizontally arranged, 'Ihecore, mounted upon pins carried by rotary end members, is adapted to bedriven through a sprocket 46 carried by one of the end members overwhich there is trained a chain 48, which extends downwardly through thetable and passes about a, sprocket 50 arranged to be driven by a motor52 through reduction gearing. The core holder, which is removable fromthe upper end of the tube 22, is provided with an anvil 96, which may beadjusted to a definite height, preferably that of a horizontal planetangent to the upper side of the core. When the core is located properlyadjacent the magnetometer, the anvil 96 abuts the lower 'end of amicrometer |00. Thus, by the proper location of the anvil with respectto the core and the adjustment of the micrometer screw, the position ofthe core with respect to the magnetic needles is determined to a highdegree of accuracy.

The recording camera is generally illustrated at II4. Itcomprisesalight-tight box IIS in .which is mounted a drum I I8 arranged to receivea sheet of photographic paper which is clamped by a clamping memberextending lengthwise of the drum. The drum is driven through reductiongearing by means of a synchronous motor I20 and its shaft is providedwith an insulating disc II'l (Figure 2) carrying a conductor I2I adaptedto engage and thereby connect with each other contact members I23.

Illumination for the magnetometer recording is provided by means of alamp |22. A beam of light from the lamp is projected to the mirror I4through an aperture in the box II6. A lengthwise extending opening isprovided in the camera box and is adapted to be covered by a shutter,which is normally in position closing the box against the entrance oflight. record is being made, this shutter is manually raised so that thebeam may enter the box.

The optical system is of substantially conventional form. The beam oflight emergingA from the box IIS passesthrough a lens |30 to the mirrorI4, by which it is reiiected back through the lens |30 and through theslot in the box. The lens I30 is a cylindrical lens having its axisvertical and is of such focal length that the beam of light intraversing it twice would be focused to a very thin vertical line at theposition of the paper on the drum II8. However, there is placed behindthe slot in the box IIE a long cylindrical condensing lens |32 having ahorizontal axis. This condensing lens is of short'focal length andserves to reduce the thin vertically extending beam which impinges uponit to a fine and very intense point of light on the sensitized paper. Asa result of this arrangement, it will be obvious that with the shutterclosed there will appear on the scale of the shutter a vertical line,and adjustment may be made using this line as a guide to the conditionof the instrument. When the shutter is open a corresponding point oflight is projected upon the paper.

In the present application the various mechanical details involved inthe apparatus and particularly in the driving of the core need not bedescribed, but reference may be had to the parent application Serial No.172,988, referred to above. Briefly stated the core is adapted to bedriven by the synchronous motor 52 in opposite directions by means of asuitable clutching arrangement.

Referring to Figure 2, it may be pointed out that driven with the gearthere is a shaft |53 carrying a serrated wheel 202, adapted to make andbreak at. 204 the circuit through transformer |92. Switch 204 is shuntedby a switch |10 connected to a reversing lever (not shown). Thisarrangement is such as to produce interruptions in the illumination ofelements I 22 and I 31 during reverse rotation but continuousillumination during forward rotation.

When a Rotated with the core there is a disc |18 of insulating materialprovided with a conductive segment |86l adapted to connect brushes |88.'Ihis arrangement is similar to that heretofore described and comprisingthe elements |2| and |23.

Power for the entire operating system is derived from an alternatingcurrent line |90. In view of the fact that both the core driving motor52 and the camera driving motor |20 are synchronous motors drivenfrom'this same line, it is obvious that the rotation of the core andcamera drum will accurately correspond. However, the core and the cameradrum are not driven at the same rotary rate. When the core makes acomplete revolution the camera drum turns through only 350. In suchfashion, a record corresponding to a complete rotation of the core isconned to a clear portion of the photographic paper on the camera drum,be-

'allowed for the overlapping and clamping of the paper thereon.

The contact members |06 and |2| of the discs |18 and ||1, respectively,are arranged to cor- 1 respond with each other to secure properoperation. The former, which may be designated the magnetometer limitingswitch is so related to the contacts |88 as to short these contactsbetween 359 and 1 of a core revolution. The zero position of a coreshould correspond to a mid-position of this shorting contact. The cameralimiting switch, on the other hand, is so arranged that the conductor|2| shorts the contacts |23 between 355 and 5 of the camera drumrotation.

The electrical relationships of the various parts will be generallyclear from the wiring diagram of Figure 2 Without detailed description.A double pole double throw switch |94 is so arranged that the motor 52may be driven for adjustment and testing purposes independently of themotor |20 or simultaneously therewith, while both are under control ofthe relay contact |96, arranged to be opened through energization of therelay coil |98. When opening of the motor circuits takes place due toenergization of the coil |90, a contact is made to energize a warningbell- 2|2, which indicates to an attendant that the determination hasbeen completed.

A transformer |92 supplies the low voltage for the energization of thelamp |22 and also for a lamp |31, which is arranged to produce a tracedown one side of the photographic paper so as to give an indication ofthe proper position of the paper when interpretations are made. A switch200 serves to control various circuits, as indicated. A

The toothed cam member 202, previously mentioned, is adapted to controla quick make and break switch 2104. The arrangement is such that duringrotation o f the cam member 202 contact is made for short periods andbroken forstill shorter periods so as to produce a dotted record on thephotographic paper. The switch |10 is arranged to short the contacts 204during a forward run, so that the record made during a forward run willbe a continuous, unbroken line, while during a reverse run, a dottedline will be produced.

Additionally, on the wiring diagram there will be noted a protectiveresistance 206 and a switch 200 serving to energize the lamps |22 and|31 independently of the rest of the apparatus.

In the use of the apparatus, the core is rst carefully prepared, forexample, by having its cylindrical face turned down and its ends groundat right angles to its axis with due precaution to avoid the inclusionin the core of any magnetic materials, such as iron chippings, or thelike. The core thus prepared is mounted in the holder and centered inpredetermined position. There is marked on the core a zero indicationfrom which angular reference about the axis may be made.

An alternative mode of preparation of the core for mounting in theapparatus is illustrated in Figure 7. It sometimes happens that cores asobtained from. a core barrel are broken and may have rather irregularsurfaces, breaks and hollows occurring along or adjacent to the lines ofseparation of the various strata. The cores in such cases may be ratherfragile and even though major breaks are mended by the use of amagnetically neutral adhesive, such as casein glue, there may be dangerof breakage if the core is subjected to turning and boring preparatoryto mounting.

Additionally, theremay be some question of demagnetization ormagnetization in a strong electric field such as that of the earth ifthe core is subjected to much shock during its preparation. The turningaccomplished by a grinding wheel may possibly aect its magneticproperties, and the same is true of the provision of holes at the endsfor mounting purposes. These various difficulties may be avoided byencasing the core in a plaster of Paris cylinder in such fashion thatthe core itself is not subjected to any appreciable vibration. case,after cementing with glue, if that ;s necessary, may be sand blasted toremove from its surface any particles of magnetic materials which it maybe carrying accidentally. The use of a sand blast, in View of theextremely small mass of the particles of sand, does not appreciablyvibrate the core to such extent as to affect its magnetic properties.Following such sand blast, the core is set up on end upon threeadjusting screws threaded into a baseboard. By the adjustment of thesescrews the axis of the core may be brought to accurate perpendicularitywith respect to the base,.whereupon it is surrounded concentrically byan internally smooth f cylindrical mold and surrounded by plaster ofParis, which is permitted to set. The mold may then be removed and theadjusting screws threaded out of the plaster of Paris with the resultthat there remains a smooth cylindrical surface concentric with the axisof the core. The plaster of Paris ends may then be bored to receive themounting and driving pins. Figure 7 illustrates a core 249 which isshown as involving various surface defects. This is surrounded by thecase 25| of plasterpf Paris, which ds bored at 253, 255 and 251 toreceive the mounting and driving pins. The screws on which the core wasoriginally supported will leave holes, as indicated at 259, but theseare of no consequence. The plaster of Paris is so soft that the mountingand driving holes may be formed therein without any substantialvibration of the core.

In making a determination the core is placed in its holder andadjustments made as described in said parent application to secureproper relative positioning of the camera and core and to insure thatthe record made by the magnetometer will be within the bounds of thecamera. A zero line is preferably traced by hand rotation of the cameradrum with the core lowered, switch 203 being closed.

With the switch |94 in its lower position, the switch 200 is closed,initiating the operation of the apparatus. At the time of thisinitiation of the operation,rit will be noted that the contacts of boththe magnetometer and camera limit switch will be closed. The contacts ofthe camera limit switch short circuit the relay coil |98 so that thelatter will not attract its armature |96 and the switch 200 will,therefore, initiate rotation of both motors 52 and |20 and will alsoenergize the transformer |92, the switch 208 being open at this time.The resistance 20E prevents a short circuit of the line. Switch |23opens the circuit before switch |88 opens its circuit, so that theoperation is not stopped.

As the core rotates, the magnet system will be deflected causing a spotof light to move across the sensitized paper on the camera. drum andthus trace a record. At the same time, the lamp4 |31 produces a markserving to indicate the right side of the photographic record. The coreis preferably Very slowly driven in order that the magnets may follow itand in order that temporary jarring of the beam of light due to causesother than the magnetic conditions of the core will fail to recordbecause the exposures corresponding to them will be very short. Sincethe clotting switch is shorted a solid line record will be made.

When the core has rotated 359 the contact |86 will bridge the contacts|88. At the same time, however, the contact |2| will not have bridgedthe contacts |23 because the camera will have rotated only about 349.Accordingly, the relay |98 is energized, opening the motor and lampcircuits and at the same time energizing the warning bell 2|2. Theoperator will then close the shutter, thus ending the record of theforward run.

The core is then removed from its support, turned end for end, andreplaced in the same position relative to the magnets as before, thisposition being determined accurately by the micrometer. The clutcharrangement is now shifted to secure a reverse rotation of the core andthe core and camera drum are reset in their zero positions as before.Simultaneously with the shift to reverse rotation the switch |10 isopened. The shutter on the camera may now be raised and the switch 200closed to provide a reversed rotation of the reversed core. The recordat this time will be dotted by reason of the interruption of the lampcircuit by the switch 204, and consequently may be later distinguishedfrom the record produced during the forward run. Automatic stoppingtakes place as before.

After development of the paper on the drum H8, the curves thereon may beinterpreted to secure the desired information relative to the magneticcharacteristics of the core. Figures 3, 4 and 5 indicate the types ofrecords which may be obtained and their interpretation, though it willbe understood that individual cores will show peculiar results in thecurves made therefrom which may have special signicance.

Consider first the Vrecord illustrated in Figure 3, made on a sheet 2M.As illustrated, this record would be of the type obtained from a coreshowing polarization only and in which the polarization was fairlyuniform. The record made during the forward run is indicated at 2|6 andthat during the reverse run at 2|0. The line 220 is the line traced bythe lamp |31 during both runs.

With a core of the type just mentioned the two curves will besubstantially symmetrically located about the mean axis. Theoretically,if uniform polarization existed a smooth sinusoidal curve would resultfrom bothruns and the two would be identical in shape but locatedoppositely on the paper. The irregularities normally obtained are due tolack of symmetry in the polarization. If polarization alone is present,the curves will intersect each other at the central axis and willexhibit a single cycle on the record sheet.

Figure 4 illustrates the type of record which would be produced from anunpolarized core, but one exhibiting anisotropic susceptibility only. Ifthe anisotropic susceptibility was of a uniform nature, exhibiting adefinite axis throughout the core, the curve to be expected on a recordsuch as that of Figure 4 would be a smooth sinusoidal curve consistingof two cycles on the length of the record. Furthermore, the recordsformed during the forward and reverse rotations would coincide.Actually, due to local irregularities, non-coincident records, asindicated at 222 and 224, will be produced, while, furthermore, thecurve will not exhibit sinusoidalsymmetry about its axis due to lack ofsymmetry of its anisotropic susceptibility about any axis.

The two records so far discussed are rather more theoretical thanactual. Actually, both polarization and susceptibility are most likelyto be present. To lexhibit the type of record obtained in such a case,and in order to make it comparable with the others, there is illustratedin Figure 5 the type of record which would result if a single core hadthe polarization which would give rise to Figure 3 if it existed alone,and the anisotropic susceptibility which would give rise to Figure 4 ifthat existed alone. It will be noted that in the case-of Figure '5, theforward and reverse curves 221 and 228 bear no recognizablelrelationship to Leach other. However, these two curves taken togethermay be interpreted to give separate information relative to polarizationand anisotropic susceptibility. Consider, for example, the spacing ofthe curves transverse to their axis at any particular point, as, forexample, at the point indicated in Figure 5 Where this spacing is 2a.One-half of this spacing, namely, a, is the corresponding deviation fromthe axis due to polarization. On the other hand, the quantity b,representing the deviation from the axis due tovanisotropicsusceptibility may be readily determined by noting the deviation fromthe axis of the center point of the line indicated at 2a in Figure 5.The gures will make clear how the two results superimpose to produce therecord of Figure 5, and how th'at record may be analyzed togive thedeviations due to the two causes. By plotting from Figure 5 the curvessuch as those in Figures 3 and 4, which are deducible from Figure 5,there may be obtained the still further information which may be derivedfrom the irregularities and lack of symmetry of these curves. Forexample, a small inclusion of a particle of magnetic material may, ifthe material is polarized, exhibit itself by a sharp deviation fromsmoothness of either one or both of the derived curves.

Another way to express the above is to say that the algebraic differenceof the curves is twice the polarization effect, and the algebraic sum ofthe curves is twice the susceptibility effect.

It will be noted that the careful marking of the core to indicate itsZero postion will enable the record to be correlated with the coreV insuch fashion that there may be marked on the core or tabulated for itthe various magnetic and susceptibility axes, and the like, which may beof interest for the purpose of interpreting the conditions of thesub-surface where the core was taken. Desirably, to determine conditionsin any local region, a number of cores from that region should beexamined so that in the interpretation only the factors common to thatregion may be given weight and proper disregard taken of the propertieswhich are solely characteristic of the individual cores. As indicatedabove, the principal matter of interest is to determine the polarizationaxis or the axis of maximum susceptibility which may'be deduced to liein the general direction of the magnetic eld of the earth. Iheorientationof strata shown in the cores may be deduced therefrom.

In Figure 6 there is illustrated 'an alternative arrangement forsecuring the type of information indicated above. In this case, theastatic magnetic system supported by a suspension wire 250 comprisesmagnets 252 and 254. A core 256, located as illustrated, with its axissubstantially parallel to the axis of the suspension, may be rotated toproduce a rst trace on the record sheet. The core is then moved to theposition indicated at 256. so that its axis is located at' a distancefrom the axis of suspension the same as before with the core at the samevertical height Y with respect to the magnetic system and at the samedistance as before from the lower magnet and similarly spaced from theopposite end of the magnet. If the core in the position 258 is on thesame side of the magnet '254 as in the position 256, its rotation shouldbe in the opposite direction to secure records of the types indicated inFigures 3 and 5. On the other hand, if it is on the opposite side of themagnet, its direction of rotation should be theI same in both cases.Under these circumstances, the results will be of the same general typeas those described heretofore, and a similar analysis may be made.

What I claim and desire to protect by Letters Patent is:

1. The method of-determining the magnetic properties of cores from boreholes comprising rotating a core about its axis adjacent a suspendedmagnetic system with at least one end of said core adjacent one pole ofthe magnetic system, noting thedefiections of said system duringrotation of the core, again rotating the core about its axis adjacentAto and similarly placed with respect to the suspended magnetic systembut with said end of said core adjacent an opposite pole of the magneticsystem, and again noting the deiiections of said system during rotationof the core.

2. The method of determining the magnetic properties of cores from boreholes comprising rotating a core adjacent to a suspended magnetic systemand about an axis perpendicular to the axis of suspension of saidsystem, noting the deflectionsof said system during rotation of thecore, changing the end for end relationship of the core and said system,again rotating the core about substantially the same axis perpendicularto the axis of suspension of said system, and again noting thedeflections of said system during rotation of the core.

3. The method of determining the magnetic properties of cores from boreholes comprising rotating a core adjacent to a suspended magnetic systemand about an axis perpendicular to the axis of suspension of saidsystem, noting the deflections of said system during rotation of thecore, changing the end for end relationships of the core and saidsystem, rotating the core in the opposite direction about substantiallythe same axis perpendicular to the axis of suspension of said system,and again noting the deflections of Said system during rotation of thecore.

4. The method of determining the magnetic properties of core from boreholes comprising rotating a core about its axis adjacent a suspendedmagnetic system with at least one end of said core adjacent one pole ofthe magnetic system, the axis of the core being parallel to the axis ofthe magnetic system, noting the deflections of said system duringrotation of the core, again rotating the core about its axis adjacent toand ,similarly placed with respect to the suspended magnetic system butwith said end of said core adjacent an opposite pole of the magneticsystem, and again noting the deflections of said system during rotationof the core.

5. The method of preparing a core from a bore hole for the determinationof its magnetic properties, comprising including said core within acylindrical cast of non-magnetic materials, with the axis of the coresubstantially coinciding with the axis 'of the cast.

6. 'I'he method of preparing a core from a bore hole for thedetermination of its magnetic properties, comprising inclu 'ng said corewithin a cylindrical cast of plaste of Paris, with the axis of the coresubstantially coinciding with the axis y of the cast.

JOHN M. PEARSON.

